Cyclophosphamide, Topotecan, and Bevacizumab (CTB) in Patients With Relapsed/Refractory Ewing's Sarcoma and Neuroblastoma

The treatment schedule for this study will consist of a 21-day cycle. Dose modification will only occur with administration of the investigational agent, bevacizumab. The schedule of administration is summarized as follows. Administration of bevacizumab will precede the administration of the cyclophosphamide and topotecan by 3 days (Day - 3) to allow for vascular stabilization prior to initiation of chemotherapy. The chemotherapy backbone will consist of cyclophosphamide and topotecan administered as follows: cyclophosphamide 250 mg/m2/day IV over 30 minutes ± 5 minutes on Days 0-4 followed by topotecan 0.75 mg/m2/day IV over 30 minutes ± 5 minutes on Day 0-4 of every cycle. The dosing of cyclophosphamide and topotecan will be fixed.